User Agent

Hello @Sven
I would like to know if a user agent is used when checking link ? 

If yes, is it unique or randomized?
When going from page to page, is the link similar to a visit?
My question comes down to whether the link is “activated” by something that looks like a normal visit for Google.

Since a lot of sites use the tracking script, Google probably comes to know if which way the visitors comes … or bots. They could be wise to modify the IP headers and even to let load the famous tracking script for Ser manual verification ….