If this will be your first mini, get a basic machine, digging bucket and grading bucket. You can worry about all the fancy attachments later. Rent them now, when you need them. Especially seeing your low budget. There really isn't a cut off year for those attachments you mentioned. You can put a quick attach on a 30 year old machine if you really wanted. Not exactly sure what 3rd hydraulics are but if i had to guess... if you look at the pictures to that machine, look at the 3rd picture. There is one hydraulic line on that side and if you look at the first picture there is regular aux hydraulics, so the "3rd hyd" is probably that one line on the one side. What its for? I have no idea, never seen it before, but its obviously for some attachment.
Personally I would never buy a mini without a thumb. Its way to useful not to have. The first time you have to stack brush or pick something up you will realize you should have gotten a machine with one.