CTI stands for Current Time Indicator, and it controls the time line of the footage in the composition panel. With the help of CTI you can move the footage backward or forward.
The time frame will be indicated with a yellow dot, by clicking on that yellow button and then pressing the delete button, you can delete the previous time frame.
Motion sketch is a path you want your object and picture to drop or move. For motion sketch, click on the window tab in menu bar and select Motion Sketch option from the window bar. Now you can draw the path and make your image move accordingly.
In edit bar, if you select split option you can split your video clip into two sections or layer. So, when you want to do animation separately for each layer or each video clip you have separated, you can do it by using split layer option.