[HELP] Help regarding SNMP

Hello everyone I got exams soon and just got some questions regarding SNMP. I have some understanding issues and would appreciate any help.

Questions:

1. Do I need a MIB Table to translate an OID to "human readable" output? or is there another way without a MIB?

2. Lets say the manufacturer of an device does not release a MIB (or you're not able to find out); and you MUST monitor a specific network device. Which steps would you take, to still monitor the device even without a MiB Table/without any translating to "human readable" information?

3. How difficult is it to create a own MIB Table to a specific device? Are the OIDs on every device the same? For example (an example i thought about) Device A - OID Sys.Info = 123 Device B - OID Sys. Info = 123 or 234? Can Device B have the same OID 123 or it can't because its alread registered for device A?

I appreciate any help. Have a nice evening everyone!!!

Thanks in advance