Normally, your tongue should touch the roof of your mouth when you pronounce the /l/ sound. The light /l/ sound and some of the dark /l/ sound, such as 'look', 'cancel', can be pronounced easily.
But the pronouncing of dark /l/ sound followed by a consonant is difficult in touching the roof of mouth, especially when I speak fast. 'twelve', 'also', 'Kelvin' are this kind of words.
So my question is as follows.
Q1. Is the action of tongue touching the roof of mouth is necessary in all situations when I pronounce /l/ sound?
Q2. When some words like 'value' are pronounced, should the /l/ sound and the /j/ sound be connected ? If they are not connected, does it mean that the action of tongue touching the roof of mouth doesn't exist? (Especially American accent.)
Thanks in advance.