Although yoga can be practiced by anyone, regardless of age, strength, flexibility, and other limitations, not all yoga classes will be suited to all people.
To get the best results for yourself, it's important to find a class that best suits your needs and interests. If you're younger and reasonably fit, and are most interested in getting a good workout, a vigorous yoga class may suit you better than a slower-paced, gentler class. On the other hand, if you're older and have limiting physical issues such as arthritis or back pain, you would most likely do much better in a slower-paced class.
When you're looking for a suitable yoga class for yourself, read the class descriptions carefully. If you still have questions about the suitability of a particular class for yourself, don't hesitate to contact the teacher.
You might discover that a number of different styles of yoga interest you and are helpful to you, or you might find that you need to be more selective in your class choice.