Is it still possible to see if you suffer from glaucoma?

Not until end stage. Glaucoma is described as the "silent blinding disease". This is because the damage is so slow that most patients do not realize that their peripheral vision is being lost. The diagnosis is made using sophisticated retinal nerve fiber layer studies, optic nerve cupping volume changes, peripheral vision changes and intraocular pressure measurements .
Yes. Depends on severity of disease. Early glaucoma can be asymptomatic, best to diagnose early and try to prevent it from worsening.
Yes. Glaucoma is usually a gradual illness that affects people's vision over a number of years. Ultimately if left untreated it can cause blindness or very decreased vision. There is a sudden onset form of glaucoma but this is usually extremely painful and makes people unwell with vomiting.
Yes. Glaucoma is a slowly progressive disease and can usually be controlled with eye drops. If glaucoma is not treated, the eye pressure can increase leading to permanent loss of vision. See your ophthalmologist is you suspect that you have glaucoma.