1- first , it's أَفْتَحُ and it's used when I'm talking about myself ( I'm opening )
2- it could be اِفْتَحْ , which is used when I'm ordering another person to open.
There's no hamza ( ء ) written in this case , yet It's still pronounced if it's in the beginning of the sentence But not if there's a conjunction letter before like ( وَافْتَحْ ) Then it's pronounced as if there wasn't any Alif there nor hamza , like ( وَفْتَحْ )
It is called wasla. It is optional and was just omitted in earlier lessons of this course.
You can put it on an alif at the beginning of a word when it does not carry hamza or madda. The alif is silent if there is a preceding vowel and instead this preceding vowel is used to connect both words in speech. You will probably not encounter it much in contemporary texts but only in القرآن and other historical texts.