this year Giro is starting in Hungary and stages are an hour riding from me so I’m planning to ride some part of the stage (last part) on a race day? Does anyone have experience with this regarding if this is allowed and is it an hour before peloton is enough?
I doubt an hour is enough. In the TdF the tour caravan comes through a long time before the front of the race does, and the roads are closed much more than an hour before the race arrives. This may be slightly different on more rural quiet roads in the countryside but certainly in cities etc you wont get on the route an hour before.
I think it takes @blind76 an hour to get to the route. Otherwise, @Bigpikle is right: better be there 2 or 3 hours before the field arrives.
PS And have fun!