[ASK] About bootloader and root.

I am new about this type of things.
so try to expain me in simple way.:p
1. Can we unlock bootloader without any software?
2.Can we root without unlocking bootloader or root without any app?
3.Can we flash ROM without rooting?
4.Or without unlocking bootloader.
5.And how to install twrp.
Thanks in advance.:)

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