For Full-timers restricted by the Schengen 90/180 rule.

[Hymerbell]

1) up to 5 years before losing the right to permanent residency** only after you have been here 5 years & have 'permanent residency** otherwise it is 2 years
2)Yes
3) If applying now before the end of the transition period then yes but it will only have a validity of 5 years.
After one year in spain you are classed as 'permanent' but not permanently permanent. This does not happen until 5 years have elapsed from original date.
During years 2 to 5 you cannot be out of spain for 2 years consecutively.
After 5 years you can exchabge your card for a new one as you are now permamently permanent & get a card for 10 years.
Now you can be out of spain for a maximum of 5 years consecutively.

if they are British citizens or hold 'permanent right of abode' then yes they can do what they want up to a maximum of 6 months consecutively. If they leave after 6 months less 1 day & then return the clock starts again.
** BUT if you have a foreign vehicle & leave after 6 months although the clock starts again for the person/s it does not for the vehicle & that has to stay out for another 6 months..

Anyone know if this is the same for Greece or just how does it work in Greece in getting a Registration Certificate and Permanent Residency Certificate....