Good luck at your rally!
The pony club rules are probably a little different from regular dressage, and we're in different countries, so take this with a big grain of salt as I am speculating:
1. The tests at training through fourth level are national level tests, FEI tests are international tests and a whole different group of tests, just for your own information

. If your rule packet says that spurs are required then wear them. If you are doing into but they are only required for training through fourth, that
to me means you don't need to wear them. That just seems really weird to me that they would be required. In Canada, spurs are optional at all levels so I don't understand why they would be required at a PC comp. But if those are the rules, those are the rules. Get really short blunt ones if you must wear them but don't want to/aren't comfortable with them.
2. I wouldn't wear a coat if it were optional! If it's option it is up to you, if you feel the need to wear one then buy one. You can usually find cheaper ones or even used coats fairly easily. At that level I would guess that many kids won't have them if they are optional.
3. We aren't allowed polo wraps and bell boots in the competition ring here in Canada. Your rules are probably the same if you recall reading that they aren't allowed.
4. I find I can retain my tests easily by just reading and riding them. Set out a little arena and practice the moves on foot - do the pattern at "walk, trot, canter" on foot. You'll look ridiculous but it works! I've also drawn them out on paper. I know of some people that read their tests out loud, record them and then listen to them over and over again.
Are you working with a coach? If you are, they should be familiar with the rules and be able to clarify some of the areas you aren't sure of. Read through the rules for the rally and any rulebooks you have. Get familiarized with them! The more you know, the better. At the show, if you run into issues and have questions on rules go ask your steward or whoever stands in as your ringkeeper-type person at the shows (I'm not sure what PC uses: actual stewards or PC volunteers etc)
I'm sorry if this was just more confusing...those are just my thoughts and it's been a long time since I was in pony club!