When switching from Reserves to active duty, how long will I have to stay active? Will I lose rank when I do the transition?

You are aware that you can't just switch over from one component to another? Your commander will have to approve a conditional release, which may not happen depending on the status of your unit. For example, if you are in a deployable unit that is cycling to AREF (Army Reserve Expeditionary Force) status, then you may be retained by your commander.

You will have to talk to a recruiter about other details. I am just taking an educated guess here, but typically, when you don't complete your contract's obligation you may have to give up remaining bonus money. But there may be a bonus for the active component position. As far as term of service, I don't know if you would have to do some version of 8 years (a combo of active and IRR time) or not. Everyone I know that crossed over lost a rank. I don't know if that would happen at E3 and below. Even if it did, it will only be a few months, typically, before you gained it back. Again, you should talk to a recruiter.

Generally, those E-4 and below retain their rank. But that is a general rule only. Although, you need to verify that with the recruiter.