Q: Is it impermissible to wear jeans during the namaz and also not to fold the jeans upto the heel?
A: Wearing these types of clothing at the time of namaaz, the clothing of kuffaar and sinners really is not in keeping with the majesty and greatness of Allah. Further, if it is just the pants that are being worn at the time of namaaz and there is no cover over it then it shows the actual shape and form of the satr. This again defeats the purpose of covering the body.
This is makrooh.
And Allah Ta’ala (الله تعالى) knows best.