He can sell it separately otherwise may have issues in pahani

Yes he can sale the land through single sale deed. The area of second plot that is 10 guntas can be demarcated in sale deed based on same the pahani will be generated. In your second plot 10 ghuntas out of thirty shall be mutated in favour of buyer. 

Separate sale deeds should be executed for 2 lands in question 

it should be duly stamped and registered 

Dear Sir,

It has a long procedure. Better create two independent sale deed. For that also katha has to be happened for 10 guntas of land after phodi.

Yes it is possible to make a simple registration for both the properties mentioning the numbers and the boundaries about both the properties which can identify the path of the Other property

Hi, you have to make phode of your survey number and the ADLR based on the survey what they have conducted  they will give new Sy No  or reassigned the Survey numbers.

No, the same will have to be sold separately 

It will not merge but two sale deed will execute. One for 20 and another for 10 gunta. In Pahani, of 30 Gunta, owner of 10 gunta will include as joint owner.

Better u seek the detailed consultation by disclosing complete details in this case, so that exactly can be suggested to do. 

He can very well sell both the landed property by a single registered sale deed. He has to demarcate the land to be sold in the other land which comprises 30 guntas to the extent he would be selling from the land.

Dear Client 

You should sale the both land through separate sales deed as it can be complicated process to first combine the plots and the sale them through single sales deed.