Only one number can be used at one time for dual SIM adapter. You need to cut the original SIM card and place in the adapter. Since you already cut the SIM card, there is no way for you to use the original SIM again without the adapter.
I have 12in1 SIM card. I don't have to cut original SIM card. What I have to do is to clone the original SIM card and put the data to my 12in1 SIM. Currently I have 9 number in one SIM. Even thou it has 9 or 12 number, I only can activate only one number at one time. Best things is I can choose which number I want to use using STK menu. The latest version of 12in1 SIM card can show which number activate by replacing the operator name with the name you put on SIM. Also it can be configure to change between 2 line automatically.