Ahhh, so the ILR must mean Indefinite Leave to Remain.
Yep - spot on

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How long is your FLR(M) good for?
FLR(M) is valid for the same amount of time as a spousal visa, but minus 3 months (because the spousal visa gives you 3 months leeway to enter the UK).
Under the old rules, the spousal visa is valid for 27 months and the FLR(M) visa is valid for 24 months. You have to spend 24 months in the UK on either visa in order to qualify for ILR.
[Under the new rules (those who applied for a spousal or fiance visa, or a first FLR(M) after July 9th 2012), the spousal visa is valid for 33 months and the FLR(M) is valid for 30 months. However, with the new rules, you have to live in the UK for 5 years to qualify for ILR, so in that case you have to apply for another 30 month FLR(M) after 30 months on either the spousal or FLR(M) visa.]
If my visa is good for 2 years, do I have to take that test at the end of that 2 years to prove I'm worthy to stay?
Yes - in order to qualify for ILR you must have:
- Lived in the UK on your spousal visa for 24 months (and still be married)
- Passed the Life in the UK test.
You can take the test at any time in the 2 years, but if you do not meet both of the above requirements before your spousal visa expires, you cannot apply for ILR and must apply for an FLR(M) visa to extend your stay in the UK until you do meet both requirements.
You said you took the online tests on the link your provided, but also read a book.
After reading the book, did you find the online test to be easy?
The test is only easy if you have read the official study guide and studied the facts in it... because all of the questions in the test are taken from the study guide.
I took a crack at the test and did okay for someone who's only lived here a few months, but not good enough.
I'm a born and raised UK citizen and when I took a practice test, I failed it spectacularly - and so do most UK citizens..... because the test isn't about how much you know about living in the UK, it's about memorising the facts in the official study guide (and I don't know the answers to half of the silly statistics questions they put in there)

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