there is no 30days tourist visa on arrival - you talk about a 30days visa excemption - and inside the country you can extens that 30 days for 1900 thb. - u need to show flyonward within 30days period, as you dont have a 60 days tourist visa - might be better to apply for that
1) yes you can - 2) in Thailand nothing is guaranteed but yes usually u get it and its not a problem - .... wondering why you been asking for a second extension?!