You get all updates as long as you keep your subscription active. Also you can install on 5 machines that are yours. I think that's how it works. And no, you don't have to renew a program if Windows breaks it. Just keep the installer packages as back ups should any get broken. If that does happen uninstall the program, use Ccleaner to get rid of any left over files, reboot your machine after the uninstall and again after you re-install it.

*maybe some clarification is necessary if I didn't get it right* 

Do i need to pay 30€ first to get object desktop and then pay 20€ every year to always get the latest updates of the programs?, or is there a cheaper way?

You have to pay the initial price for Object Desktop, then renew each year at a discounted renewal rate.

After a major update you would. EX: It's been 2 years for Windowblinds and no major update. A major update is when the number before the decimal changes. EX: windowblinds 10.0. It's now at 10.65. So as I said over two years now. Could happen in a month as there is no real time line so to speak. 

As mentioned if you renew Object Desktop each year you always get the updates no matter what version number. Many people run into problems because they don't download the actual .exe installers from the Stardock store. do this and make sure you have the serial number or key and you will always have it. Many old versions still work on newer OS changes. If people don't save the older .exe programs they will not be available forever.

Is it true what uvah saied that you can install the programs on up to 5 devices, and can i install it on a new one if i uninstall it on an other one?