Badfinger78

Hello All,
I have a 97 Vento GL,2.0,Automatic,front wheel drive.
(1)Sometimes when driving between 35-40 kph my Rpm needle sticks on 3 for a good couple seconds as well as the speedometer stays at the same speed even tho I am gassing it????..It sounds awful until it finally clears(2)Why does my Rpm needle jump up and down when I turn on my A/C while rolling in traffic???? (3) also is the cooling system totally different from Japanese cars? I notice sometimes my needle moves past the halfway mark which is 90 on the meter and settles at 100????is that normal?
Any advice appreciated...Thanks!