As you have asked 2 questions, I’ll answer them in 2 separate postings.
To deal with the vocabulary question, you could give you students a text with the unknown or difficult words blanked out or crossed out. By doing this, the students just don’t see the words; they won’t know what to look up in the dictionary or what to ask.
It’s important to train students in how to deal with unknown words. You could spend some time in class showing them how to do this. You could take a sentence with a nonsense word and ask them to guess the meaning.
For example: Mr Jones, came home, walked into the kitchen and put his books on the mosty.
Ask students questions such as:
“is mosty a noun, verb, adjective….?”
Where can you find a mosty? (In the home, in the kitchen).
Can you guess what category a mosty belongs to? (In this sentence, mosty is probably a piece of furniture).
Think about when you go home, where do you place your books? On the table, on a chair.
Explain to them that in order to understand the sentence, it is enough to know that a mosty is a piece of furniture found in a kitchen. As you rightly say, students can guess this from context.
Do three or four examples together as a whole class then ask students to work in pairs on other sentences containing nonsense words. If you find that your students are asking about the nonsense words, stop what you are doing and tell them all to look the words up in their dictionaries. When they realise that the words aren’t there, they’ll understand that they need to use other strategies to work out the meanings. Do some feedback as a whole class and ask students what they think the words mean and how they came to that conclusion.
In later lessons, when you work on a text, you can tell your students that they can look up 6 words (for example) in their dictionaries. Tell them to go through the text and to decide carefully which words they would like to look up. This will encourage them to decide which words they can guess from context and which are more difficult to deduce and require the use of a dictionary.