Need some advice about requesting recommendation letters

I'm applying to a master's program at the moment, and it's time that I go ahead and send out recommendation letter request emails. It's been a while since I last did this - I completed my first master's program in 2017 and haven't kept in contact with/ anyone from the program really - the last time I talked to anyone was probably within 6 months after I graduated. I'm planning to request at least one recommendation letter from one of my intern supervisors/professors from my previous program. Every example of what to put in the email seems long to me - can the initial request for a recommendation be fairly brief? I was just planning on letting them know what I've been up to, what kind of programs I'm applying to, and the # of programs when they'd be due. Should I tell them if there's any information they need to answer any questions in the recommendation form/letter, I can provide it if needed?

Another thing is, this time, I'm applying to online programs, which I've never done before. Some of the applications can be submitted whenever, and if accepted I'd just begin the program during the next available term, which may be sometime in Spring or the summer, so is it okay if I just say that I'd just need it completed by some random date I decide on? I just thought about just telling them I'd give them a heads up once the link would be sent to them and give them a time frame, but it's just weird to me because the last time I applied to traditional programs I knew exactly what to tell them, with exact dates.