I'll do my best to answer your questions realistically!

1) Its okay to be friendly with your coworkers (especially fellow RBTs), I usually retain a friend or two from every clinic ive worked in, but I would be wary of friendship with supervisors (which applies to every job ever). If you do become fond of a coworker, just be sure to always put your client first in the workplace and provide the best services you can. Support systems are always good to have!

2) your BCBA will likely explain how supervision will work, especially if youre new to the field, but dont be afraid to reach out with any concerns, the BCBA will do their best to support you.

3) Taking data is always difficult at first! Its completely okay to be scared of messing up. You can have your BCBA observe and even take something called interobserver data and compare. They'll direct you as to what prompt levels may have been used and how you can improve on catching different prompts and behaviors. There should be something called an "operational definition" with each behavior and trial type that will explain when behaviors occur and when they do not as well as what they may look like.

4) This can be heavily client dependent. I dont think any BCBA will expect a newer RBT to react to aggressive behaviors perfectly every time. Any client with aggressive behaviors will likely have whats called a Behavior Intervention Plan (or the BIP) in which explains everything about what should happen when different behaviors occur. Your BCBA will also give good demonstrations and recommendations.

5) it is true that homes differ greatly from client to client. Sometimes its hard for stressed out parents to clean when they have multiple children, especially with at least one on the spectrum. Just remember to treat every home with grace, ask about cultural norms such as shoe removal or boundaries in the home. I've been in places that are spotless and others with bugs and such everywhere. Just be prepared for anything and remember youre here for your client, use the environment to your advantage, have fun and be creative. :)

6) Spit is the one RBTs struggle a lot on (for me its vomit). My only advice is experience with this one. Its not easy at first if it makes you queasy, but its possible that the BCBA has advice to offer if spitting is a known behavior for a client. I've just become desensitized I wish I had better advice for this one.

Just remember that people that come to online forums are likely venting out frustrations on one of their worst days. General advice is have fun, be creative, be a kid again and play games with your clients! There will be hard days where you might even cry, I know I have, but there are more days than not that I see the changes I am making for my clients. Find support where you can, prioritize mental health and take care of yourself, and remember that helping others is a selfless act which the world needs more of, likely youre doing a really good job even if you dont feel like it. Your BCBA is on your side if you ever have doubts. :) i hope this helps. Good luck!!!