1) Yes, you can defer using the credit for as many years as you want.
2) Yes, your generated RRSP room never disappears until you use it (contribute), but when you hit age 71 (or your spouse hits 71 if you have a spousal RRSP) you can't actually use it any more.
3) Yes, you can have an RRSP and RRIF at the same time until you hit age 71. Also, you can convert a portion of your RRSP into a RRIF and keep your old RRSP going, if that is useful, up until age 71.
Even if your tax bracket in the contribution year and withdrawal year is the same, you get growth inside your RRSP without yearly tax-drag. The TFSA is more flexible if you anticipate that scenario, but RRSP works OK if you have already used all your TFSA room.
Edit: You may have a strategy in mind, but withdrawing from RRIF and contributing to RRSP in the same year seems like an unusual idea. I am curious what your thoughts are for that?