MicrostockGroup

You can upload to tons of sites RF. I'm sure people will chip in if there's any who don't allow it. For someone starting out, it's probably now better to play the field; different sort of shots may sell better at different agencies. Again, it's your tolerance of time/effort vs payout which will determine whether it's 'worth it' for you. Start with iStock and Shutterstock to begin with.
Be sure to read every site's terms and conditions carefully, especially with regard to how long your files are locked in for (from 0 days up to 6 months) if that might bother you. Also sometimes sites can hive your files off to partner sites, which (I have read here) can be difficult to extricate yourself from, should you wish to.

Good luck! You'll probably need it.

1.  Yes, you can.
2.  Yes, it is ok.
3.  No idea.
4.  Be aware it will take you up to 6 months to turn exclusive once you decide to.  I don't think I'd recommend exclusivity to newbs - there's too many issues currently.

You could put stuff up on Alamy but they have their own strange criteria for the size of the photos you upload to them.  I would go read in the Alamy forum on here for more specifics.  They don't want to much touching up and a bunch of other things that I don't remember because none of my photos will upload there.  Just do some reading and then decide for yourself if you want to upload to them.

It is definitely up to you on how many sites you want to spread your work out to.  And how much time you want to spend uploading.  Just for an example I'm on currently 14 sites, I've stopped uploading to 4 of them for various reasons, which leaves me with 10 (one's a video site that I've negleted for months) so in effect out of those I only upload to 9 and depending on the time of day can take me up to 2 hours to upload 10 images across all of those sites.

I'm sure you'll do fine in whatever you decide to do.

Yeah Sue that's why none of my photos will upload.  Eventhough my camera is on their accepted list and I have to fiddle with it in photoshop to get rid of sensor dust the size of my file is no longer big enough to upload to there.  Could try a test one where I save it as a psd then make the jpg out of that and see if it works but that makes an extra step that I don't wanna deal with.

Really?  I didn't think I could because I thought it was a big no-no everywhere.

Two answers, one you already have, it's just a slight additional bit.

RF sites, you have three choices, (opinion alert) 1) Exclusive (DT, FT, or IS), 2) SS and IS only, 3) As many sites as you can find that will take your work, 25 and up is just a start. Everything, everywhere! Shotgun approach and it works.

Part two: Alamy is not Microstock. (broken record alert) The same best sellers on Micro may sit forever and never make a sale on Alamy. Yes, depending on the subject and the image, Alamy can be good. The flip side of the coin is things that won't get accepted anywhere on any Micro site, might sell on Alamy. Different market, different buyers.

And the next thing people ask is how many pictures do I need to have on Alamy before I make a sale. It has nothing to do with "how many" it's what are they pictures of. It's not micro where you get multiple sales. Sometimes on Alamy one sale is worth 300 Microstock sales.