• Participants must have histologically confirmed NSCLC and measurable disease by RECIST v1.1. Note: Participants in Cohorts 1, 5 and 11 do not have to present with measurable disease.

‣ Participants must present with unresectable Stage III or metastatic Stage IV NSCLC by American Joint Commission on Cancer (AJCC) Cancer Staging Manual, Eighth Edition.

‣ EXCEPT

⁃ Participants in Cohorts 5 and 11 must present with unresectable Stage III NSCLC by AJCC Cancer Staging Manual, Eighth Edition before receiving pre-trial chemoradiotherapy.

⁃ Participants in Cohort 6 with the initial diagnosis of resectable Stage II and Stage III NSCLC by AJCC Cancer Staging Manual, Eighth Edition.

• Participants in Cohorts 2, 4, 5, 6, 10 and 11 must be able to tolerate (additional) anti-PD-1 therapy (i.e., did not permanently discontinue anti-programmed death protein 1 \[PD-1\] / programmed death ligand 1 \[PD-L1\] therapy due to toxicity).

• Participants must have an Eastern Cooperative Oncology Group performance status (ECOG-PS) less than or equal to (\<=) 1, except for participants in Cohorts 1, 4, 5, 10 and 11 who are eligible with an ECOG-PS of 0-2.

∙ Cohort-specific inclusion criteria:

∙ Cohort 1:

• Participants prior therapy must have included at least a PD-1/PD-L1 inhibitor and a platinum-based chemotherapy regimen as well as one other line of systemic therapy (except if a participant is not candidate for a platinum-based chemotherapy and/or PD-1/PD-L1 inhibitor and/or another line of systemic therapy). Note: Participants newly enrolled in Cohort 1B under protocol v 5.0 and subsequent versions of the protocol must consent to mandatory blood sampling for peripheral blood mononuclear cells (PBMCs).

• Participants who are to start cemiplimab at Cycle 3 must present with PD-L1 expression of tumor proportion score (TPS) greater than or equal to (\>=) 1% in tumor cells (as determined locally).

∙ Cohort 2:

• Participants must present with PD-L1 expression of tumor proportion score (TPS) \>= 50% in tumor cells (as determined locally prior to inclusion in this trial).

• Participants must present with progressive disease either

‣ in the advanced or metastasized stage of NSCLC: while on a PD-1/PD-L1 inhibitor therapy or within 6 months of termination of this treatment as first-line treatment. Or

⁃ be refractory to ongoing adjuvant therapy/maintenance treatment after CRT with a PD-1/PD-L1 inhibitor that has been given for at least 3 months in monotherapy (i.e., after an initial combination therapy) before being enrolled into this trial.

∙ Cohort 3:

• Participants prior therapy must have included at least a PD-1/PD-L1 inhibitor and a platinum-based chemotherapy regimen (except if a participant is not candidate for a platinum-based chemotherapy and/or PD-1/PD-L1 inhibitor).

• Participants must present with progressive disease.

∙ Cohort 4:

• Participants who are not candidates for chemotherapy as first-line treatment for the advanced or metastasized stage of NSCLC may be enrolled if presenting with PD-L1 expression: TPS \>= 1% in tumor cells (as determined locally).

∙ Cohort 5:

• Participants NSCLC must have been considered unresectable due to participant's condition and/or tumor-related factors and the participants must have undergone chemoradiotherapy before entering the trial.

∙ Cohort 6:

• Participants NSCLC must be considered technically and medically resectable.

• Participants must be considered eligible for neo-adjuvant treatment.

∙ Cohort 7:

• Participants prior therapy must have included at least a PD-1/PD-L1 inhibitor and a platinum-based chemotherapy regimen (except if a participant is not a candidate for a platinum-based chemotherapy and/or PD-1/PD-L1 inhibitor). Note 1: Participants may have received prior therapy targeting CTLA-4, lymphocyte-activation gene 3 (LAG-3), T cell immunoglobulin and immunoreceptor tyrosine-based inhibitory motif \[ITIM\] domain (TIGIT), VEGF or VEGF receptor (VEGFR) inhibitor as monotherapy or part of a combination therapy. Note 2: If the participants' prior therapies included a CTLA-4 inhibitor, the participant must be able to tolerate (additional) treatment with the CTLA-4 inhibitor.

• Participants must present with progressive disease at trial enrollment.

• Participants must consent to mandatory blood sampling for PBMCs.

∙ Cohorts 8 \& 9:

• Participants prior therapy must have included at least a PD-1/PD-L1 inhibitor and a platinum-based chemotherapy regimen (except if a participant is not a candidate for a platinum-based chemotherapy and/or PD-1/PD-L1 inhibitor).

• Participants must present with progressive disease at trial enrollment.

∙ Cohort 10:

• Participants who are not candidates for chemotherapy as first-line treatment for the advanced or metastasized stage of NSCLC may be enrolled.

∙ Cohort 11:

• Participant's NSCLC must have been considered unresectable due to participants condition and/or tumor related factors and the participants must have undergone chemoradiotherapy before entering the trial.