Hey apoorva

You forgot to mention  your board for HSC. It is important because the schedule is different for cbse and state boards.

However I can anser the latter half of your question. The pocedure for late admission in degree colleges (BPT) is same as that of regular admission (unless you have not passed in pcb subjects in your 12th) as:

You need to pass in your HS exam with minimum 50% in PCB

You can give different CETs in which you need to pass . Admission is based on the CET score.

Then comes the age barrier. You should be minimum 17 yeards old to apply. As for the "late: admission is concerned, it does not happen after the classes have started in most colleges (unless you have a source or you are taking admission in a private college like LPU or Amity where they might consider your late application). All the best.