A 1.5 hour ride is pretty long here, and you might find that you’ll need more rest between intense sessions. Amateurs, in general, fail to rest/recover enough—I always err on the side of too much recovery vs too little.
Not necessarily, and usually not. More often than not you’ll focus on working the same “system” (ex: threshold or VO2 or anaerobic) for that 4-week block and then decide whether or not you want to continue or change it up.
For example, I don’t and wouldn’t suggest you do a block of work that focuses on increasing FTP that includes work right around threshold (ex: 3x12 min @ 95%) and then have your next workout focus in anaerobic capacity (ex: 6x1 min @ 150%). That likely won’t be productive.
Note: everything under anaerobic is working the aerobic system to varying degrees.
Tapering is something that takes trial and error. Taper too long and you’ll loose too much fitness. Taper too short and you won’t lose enough fatigue. Personally, I like tapering 5-7 days before an event. Cut volume by half (or more depending) but include a couple days of intensity. I always like a day off the bike 2 days before my event.