Modelagem

Question 1

Edit mode, face selection, hold shift, select multiple faces.

Answer 1

Click extrude region, drag the gizmo plus down.
Activate the move tool, change to edge select, select the blue arrow.
Select menu, all, mesh menu, Symmetrize. On the Symmetrize menu, change to +X to -X.

Question 2

Referência: back face culling(seta a direita), object data properties, side, front. Alt+z, objeto fica transparente.

Answer 2

Loop cut coloca vertices, colocar poucos.
Edit mode, selecionar vertices, G e mover.
Colocar modificador subdivision.
Trabalhar com o inseto, extrude.
Adicionar o simple deform. Shade smooth, botão da direita.