HI Ronak,
1. The default SmartGrid doesn’t support the functionality you need, but the Tree Grid has the exact functionality as described by you.
Please, take a look at this demo: https://www.htmlelements.com/angular/demos/grid/tree-grid-checkbox/
2. For this inquiry you can set the ‘selection’ property and its mode to extended like so:
//In your app.components.ts file for example

selection = {
  enabled: true,
  allowCellSelection: true,
  mode: 'extended',

//in your app.component.html file:

<smart-grid #grid id="grid" [behavior]="behavior" [selection]="selection" [checkBoxes]="checkBoxes"
    [dataSource]="dataSource" [columns]="columns" [filtering]="filtering"  [editing]="editing" >

Also you can check out this demo regarding the selection: https://www.htmlelements.com/angular/demos/grid/selection-mode-row/
Let me know if that works for you!
Please, do not hesitate to contact us if you have any additional questions.
Best regards,
Yavor Dashev
Smart UI Team